upgrade iPhone without SIM card?

It will need to be activated with a sim card after you update. I upgraded my girlfriends iPhone 3G from 4.0 to 4.0.1 and it popped up the connect to iTunes screen. I was using redsn0w though and it let me do a hactivation and I was able to bypass iTunes and get into the OS without a sim card. I don't know if those programs work with the 3GS right now and I have no idea about Jailbreakme.com. (http://wikee.iphwn.org/howto:rs9). Anyway, from the quick read that I did it appears that it would work for you, but you would have to have an early model 3GS. Late models would have problems like tethered rebooting and ****. Not sure though.

Also if you do the hacktivation method, youtube and push notifications won't work. You'll have to add this repo in Cydia: http://www.cmdshft.ipwn.me/apt/ and install Push Doctor to get the certs. Make sure you do this before you install any applications that require Push notifications otherwise you'll have to reinstall them all.

According to this thread it might not work seems ambiguous: http://www.hackint0sh.org/f148/55456.htm

iunnohead said:

no the SIM card is activated, i'm just not using it because i'm traveling and don't want to pay for roaming; it is still being paid for though

Click to expand...

Oh in that case yeah you can probably use it. Just activate and pull the sim card out and it should go back to being used as an iPod Touch. The only thing you really need the sim card for other than calling and data is to get past that connect to iTunes screen on a freshly restored phone. Although everytime you reboot your phone it'll pop up this message that says no sim card found or something like that. You can fix that message though by using sbsettings and turning all the data and phone toggles to off. Or just deal with the message it only pops up after you reboot or respring and goes away once you hit the ok button.